The floating ice shelves of northern Greenland, whose role is crucial in regulating the quantity of fresh water discharged into the ocean, have lost more than a third of their volume since 1978, warn scientists in a study published Tuesday .
Researchers based in Denmark, the United States and France used thousands of satellite images, combining them with field measurements and models to reconstruct the evolution of these platforms that extend glaciers onto the water.
“Since 1978, the ice shelves of North Greenland have lost more than 35% of their total volume, with three of them completely collapsing,” out of the eight present in the region, the authors conclude in the journal Nature Communications.
“The main reason is that they melted below with the warming of ocean waters,” Romain Millan, researcher at CNRS and the University of Grenoble, lead author of the study, explains to AFP.
“We have highlighted a very significant increase in melting since the 2000s, which obviously corresponds to the increase in ocean temperatures in this sector and during this period,” he indicates.
The melting of these platforms does not directly contribute to the rise in ocean levels.
On the other hand, these platforms play the role of a “dam” regulating the quantity of frozen fresh water coming from the cap dumped into the ocean and which, in turn, contributes to this phenomenon.
The disappearance of these natural dams therefore has significant effects on glaciers, whose anchor points on the ground are retreating and which are dumping more ice than before.
“For example, the Zachariae Isstrøm glacier, which lost its platform in 2003, then almost doubled the quantity of ice it discharged into the ocean,” notes Romain Millan.
These conclusions are all the more alarming since the glaciers in this region were until now considered stable by scientists, unlike other more sensitive areas of the polar cap which began to weaken in the mid-1980s.
“What will happen at the poles and sea levels in the future will depend on the decisions that will be taken by politicians to reduce greenhouse gas emissions,” recalls the researcher a few weeks before COP28 on the climate in Dubai (November 30-December 12).